Systems and methods for restoring muscle function to the lumbar spine

ABSTRACT

A system for restoring muscle function to the lumbar spine to treat low back pain is provided. The system may include electrodes coupled to an implantable pulse generator (IPG), a handheld activator configured to transfer a stimulation command to the IPG, and an external programmer configured to transfer programming data to the IPG. The stimulation command directs the programmable controller to stimulate the tissue in accordance with the programming data. The system may include a software-based programming system run on a computer such that the treating physician may program and adjust stimulation parameters.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/299,399, filed Oct. 20, 2016, which is a continuation of U.S. patent application Ser. No. 14/792,430, filed Jul. 6, 2015, now U.S. Pat. No. 9,474,906, which is a continuation of U.S. patent application Ser. No. 14/061,614, filed Oct. 23, 2013, now U.S. Pat. No. 9,072,897, which is a continuation-in-part application of U.S. patent application Ser. No. 13/858,809, filed Apr. 8, 2013, now U.S. Pat. No. 8,606,358, which is a continuation of U.S. patent application Ser. No. 12/075,174, filed Mar. 10, 2008, now U.S. Pat. No. 8,428,728, which claims the benefit of priority of U.S. Provisional Application Ser. No. 60/905,979, filed Mar. 9, 2007, the entire contents of each of which are incorporated herein by reference.

II. FIELD OF THE INVENTION

This application generally relates to systems and methods for neuromuscular electrical stimulation, including stimulation of tissue associated with control of the lumbar spine for treatment of back pain.

III. BACKGROUND OF THE INVENTION

The human back is a complicated structure including bones, muscles, ligaments, tendons, nerves and other structures. The spinal column has interleaved vertebral bodies and intervertebral discs, and permits motion in several planes including flexion-extension, lateral bending, axial rotation, longitudinal axial distraction-compression, anterior-posterior sagittal translation, and left-right horizontal translation. The spine provides connection points for a complex collection of muscles that are subject to both voluntary and involuntary control.

Back pain in the lower or lumbar region of the back is common. In many cases, the cause of back pain is unknown. It is believed that some cases of back pain are caused by abnormal mechanics of the spinal column. Degenerative changes, injury of the ligaments, acute trauma, or repetitive microtrauma may lead to back pain via inflammation, biochemical and nutritional changes, immunological factors, changes in the structure or material of the endplates or discs, and pathology of neural structures.

The spinal stabilization system may be conceptualized to include three subsystems: 1) the spinal column, which provides intrinsic mechanical stability; 2) the spinal muscles, which surround the spinal column and provide dynamic stability; and 3) the neuromotor control unit, which evaluates and determines requirements for stability via a coordinated muscle response. In patients with a functional stabilization system, these three subsystems work together to provide mechanical stability. It is applicant's realization that low back pain results from dysfunction of these subsystems.

The spinal column consists of vertebrae and ligaments, e.g. spinal ligaments, disc annulus, and facet capsules. There has been an abundance of in-vitro work in explanted cadaver spines and models evaluating the relative contribution of various spinal column structures to stability, and how compromise of a specific column structure will lead to changes in the range of motion of spinal motion segments.

The spinal column also has a transducer function, to generate signals describing spinal posture, motions, and loads via mechanoreceptors present in the ligaments, facet capsules, disc annulus, and other connective tissues. These mechanoreceptors provide information to the neuromuscular control unit, which generates muscle response patterns to activate and coordinate the spinal muscles to provide muscle mechanical stability. Ligament injury, fatigue, and viscoelastic creep may corrupt signal transduction. If spinal column structure is compromised, due to injury, degeneration, or viscoelastic creep, then muscular stability must be increased to compensate and maintain stability.

Muscles provide mechanical stability to the spinal column. This is apparent by viewing cross section images of the spine, as the total area of the cross sections of the muscles surrounding the spinal column is larger than the spinal column itself. Additionally, the muscles have much larger lever arms than those of the intervertebral disc and ligaments.

Under normal circumstances, the mechanoreceptors exchange signals with the neuromuscular control unit for interpretation and action. The neuromuscular control unit produces a muscle response pattern based upon several factors, including the need for spinal stability, postural control, balance, and stress reduction on various spinal components.

It is believed that in some patients with back pain, the spinal stabilization system is dysfunctional. With soft tissue injury, mechanoreceptors may produce corrupted signals about vertebral position, motion, or loads, leading to an inappropriate muscle response. In addition, muscles themselves may be injured, fatigued, atrophied, or lose their strength, thus aggravating dysfunction of the spinal stabilization system. Conversely, muscles can disrupt the spinal stabilization system by going into spasm, contracting when they should remain inactive, or contracting out of sequence with other muscles. As muscles participate in the feedback loop via mechanoreceptors in the form of muscle spindles and golgi tendon organs, muscle dysfunction may further compromise normal muscle activation patterns via the feedback loops.

Trunk muscles may be categorized into local and global muscles. The local muscle system includes deep muscles, and portions of some muscles that have their origin or insertion on the vertebrae. These local muscles control the stiffness and intervertebral relationship of the spinal segments. They provide an efficient mechanism to fine-tune the control of intervertebral motion. The lumbar multifidus, with its vertebra-to-vertebra attachments is an example of a muscle of the local system. Another example is the transverse abdominus, with its direct attachments to the lumbar vertebrae through the thoracolumbar fascia.

The multifidus is the largest and most medial of the lumbar back muscles. It has a repeating series of fascicles which stem from the laminae and spinous processes of the vertebrae, and exhibit a constant pattern of attachments caudally. These fascicles are arranged in five overlapping groups such that each of the five lumbar vertebrae gives rise to one of these groups. At each segmental level, a fascicle arises from the base and caudolateral edge of the spinous process, and several fascicles arise, by way of a common tendon, from the caudal tip of the spinous process. Although confluent with one another at their origin, the fascicles in each group diverge caudally to assume separate attachments to the mamillary processes, the iliac crest, and the sacrum. Some of the deep fibers of the fascicles that attach to the mamillary processes attach to the capsules of the facet joints next to the mamillary processes. The fasicles arriving from the spinous process of a given vertebra are innervated by the medial branch of the dorsal ramus that issues from below that vertebra.

The global muscle system encompasses the large, superficial muscles of the trunk that cross multiple motion segments, and do not have direct attachment to the vertebrae. These muscles are the torque generators for spinal motion, and control spinal orientation, balance the external loads applied to the trunk, and transfer load from the thorax to the pelvis. Global muscles include the oblique internus abdominus, the obliquus externus abdmonimus, the rectus abdominus, the lateral fibers of the quadratus lumborum, and portions of the erector spinae.

Normally, load transmission is painless. Over time, dysfunction of the spinal stabilization system is believed to lead to instability, resulting in overloading of structures when the spine moves beyond its neutral zone. The neutral zone is a range of intervertebral motion, measured from a neutral position, within which the spinal motion is produced with a minimal internal resistance. High loads can lead to inflammation, disc degeneration, facet joint degeneration, and muscle fatigue. Since the endplates and annulus have a rich nerve supply, it is believed that abnormally high loads may be a cause of pain. Load transmission to the facets also may change with degenerative disc disease, leading to facet arthritis and facet pain.

For patients believed to have back pain due to instability, clinicians offer treatments intended to reduce intervertebral motion. Common methods of attempting to improve muscle strength and control include core abdominal exercises, use of a stability ball, and Pilates. Spinal fusion is the standard surgical treatment for chronic back pain. Following fusion, motion is reduced across the vertebral motion segment. Dynamic stabilization implants are intended to reduce abnormal motion and load transmission of a spinal motion segment, without fusion. Categories of dynamic stabilizers include interspinous process devices, interspinous ligament devices, and pedicle screw-based structures. Total disc replacement and artificial nucleus prostheses also aim to improve spine stability and load transmission while preserving motion.

There are a number of problems associated with current implants that aim to restore spine stabilization. First, it is difficult to achieve uniform load sharing during the entire range of motion if the location of the optimum instant axis of rotation is not close to that of the motion segment during the entire range of motion. Second, cyclic loading of dynamic stabilization implants may cause fatigue failure of the implant, or the implant-bone junction, e.g. screw loosening. Third, implantation of these systems requires surgery, which may cause new pain from adhesions, or neuroma formation. Moreover, surgery typically involves cutting or stripping ligaments, capsules, muscles, and nerve loops, which may interfere with the spinal stabilization system.

Functional electrical stimulation (FES) is the application of electrical stimulation to cause muscle contraction to re-animate limbs following damage to the nervous system such as with stroke or spine injury. FES has been the subject of much prior art and scientific publications. In FES, the goal generally is to bypass the damaged nervous system and provide electrical stimulation to nerves or muscles directly which simulates the action of the nervous system. One lofty goal of FES is to enable paralyzed people to walk again, and that requires the coordinated action of several muscles activating several joints. The challenges of FES relate to graduation of force generated by the stimulated muscles, and the control system for each muscle as well as the system as a whole to produce the desired action such as standing and walking.

With normal physiology, sensors in the muscle, ligaments, tendons and other anatomical structures provide information such as the force a muscle is exerting or the position of a joint, and that information may be used in the normal physiological control system for limb position and muscle force. This sense is referred to as proprioception. In patients with spinal cord injury, the sensory nervous system is usually damaged as well as the motor system, and thus the afflicted person loses proprioception of what the muscle and limbs are doing. FES systems often seek to reproduce or simulate the damaged proprioceptive system with other sensors attached to a joint or muscle.

For example, in U.S. Pat. No. 6,839,594 to Cohen, a plurality of electrodes are used to activate selected groups of axons in a motor nerve supplying a skeletal muscle in a spinal cord patient (thereby achieving graduated control of muscle force) and one or more sensors such as an accelerometer are used to sense the position of limbs along with electrodes attached to muscles to generate an electromyogram (EMG) signal indicative of muscle activity. In another example, U.S. Pat. No. 6,119,516 to Hock, describes a biofeedback system, optionally including a piezoelectric element, which measures the motions of joints in the body. Similarly a piezoelectric crystal may be used as a muscle activity sensor as described by U.S. Pat. No. 5,069,680 to Grandjean.

FES has also been used to treat spasticity, characterized by continuous increased muscle tone, involuntary muscle contractions, and altered spinal reflexes which leads to muscle tightness, awkward movements, and is often accompanied by muscle weakness. Spasticity results from many causes including cerebral palsy, spinal cord injury, trauma, and neurodegenerative diseases. U.S. Pat. No. 7,324,853 to Ayal describes apparatus and method for electrically stimulating nerves that supply muscles to modify the muscle contractions that lead to spasticity. The apparatus includes a control system configured to analyze electrical activity of one or more muscles, limb motion and position, and mechanical strain in an anatomical structure.

Neuromuscular Electrical Stimulation (MMES) is a subset of the general field of electrical stimulation for muscle contraction, as it is generally applied to nerves and muscles which are anatomically intact, but malfunctioning is a different way. LAMES may be delivered via an external system or, in some applications, via an implanted system.

LAMES via externally applied skin electrodes has been used to rehabilitate skeletal muscles after injury or surgery in the associated joint. This approach is commonly used to aid in the rehabilitation of the quadriceps muscle of the leg after knee surgery. Electrical stimulation is known to not only improve the strength and endurance of the muscle, but also to restore malfunctioning motor control to a muscle. See, e.g., Gondin et al., “Electromyostimulation Training Effects on Neural Drive and Muscle Architecture”, Medicine & Science in Sports & Exercise 37, No. 8, pp. 1291-99 (August 2005).

An implanted NMES system has been used to treat incontinence by stimulating nerves that supply the urinary or anal sphincter muscles. For example, U.S. Pat. No. 5,199,430 to Fang describes implantable electronic apparatus for assisting the urinary sphincter to relax.

The goals and challenges of rehabilitation of anatomically intact (i.e., non-pathological) neuromuscular systems are fundamentally different from the goals and challenges of FES for treating spinal injury patients or people suffering from spasticity. In muscle rehabilitation, the primary goal is to restore normal functioning of the anatomically intact neuromuscular system, whereas in spinal injury and spasticity, the primary goal is to simulate normal activity of a pathologically damaged neuromuscular system.

It would therefore be desirable to provide an apparatus and method to rehabilitate muscle associated with control of the lumbar spine to treat back pain.

It further would be desirable to provide an apparatus and method to restore muscle function of local segmental muscles associated with the lumbar spine stabilization system.

IV. SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of previously-known systems by providing systems and methods for restoring muscle function to the lumbar spine to treat, for example, low back pain. The system may include one or more electrodes coupled to an implantable pulse generator (IPG), a handheld activator configured to be wirelessly coupled to the IPG, and an external programmer configured to be wirelessly coupled to the IPG. The one or more electrodes are configured to be implanted in or adjacent to tissue associated with control of the lumbar spine. The IPG is coupled to the one or more electrodes, and preferably includes a programmable controller and a first communications circuit. The handheld activator includes a second communications circuit and is configured to transfer a stimulation command to the IPG via the first and second communications circuits. The external programmer has a third communications circuit and is configured to transfer programming data to the IPG via the first and third communications circuits. The stimulation command may direct the programmable controller to stimulate the tissue in accordance with the programming data.

The external programmer may be coupled to a computer, e.g., a physician's computer, configured to run software. The software preferably causes the programming data to be displayed, e.g., on the computer's display, and permits selection and adjustment of such programming data based on user input.

The programming data transferred between the external programmer and the IPG preferably includes at least one of: pulse amplitude, pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, or electrode configuration. For example, a physician may adjust a stimulation rate or cause a treatment session to be started on the external programmer or on the programming system software via the computer and programming data will be sent to the IPG to execute such commands.

The stimulation commands transferred between the activator and the IPG preferably include at least one of: a command to start a treatment session or stop the treatment session; a command to provide a status of the implantable pulse generator; or a request to conduct an impedance assessment. For example, a user, e.g., physician, patient, caretaker, may cause a treatment session to be started on the activator and a command will be sent to the IPG to execute such command. The activator may have a user interface configured to receive user input to cause a stimulation command to be generated.

The one or more electrodes are configured to be implanted in or adjacent to at least one of nervous tissue, a muscle, a ligament, or a joint capsule. The system may include a lead coupled to the IPG and having the electrode(s) disposed thereon. The lead may be coupled to a first fixation element configured to anchor the lead to an anchor site, e.g., muscle, bone, nervous tissue, a ligament, and/or a joint capsule. The lead may be further coupled to a second fixation element, distal to the first fixation element. In one embodiment, the first fixation element is angled distally relative to the lead and the second fixation element is angled proximally relative to the lead such that the first and second fixation elements are configured to sandwich the anchor site therebetween.

The programmable controller of the IPG may be programmed with, for example, stimulation parameters and configured to adjust stimulation parameters based on receipt of programming data from the external programmer. In one embodiment, the programmable controller is programmed to direct the one or more electrodes to stimulate the tissue at a pulse amplitude between about 0.1-7 mA or about 2-5 mA, a pulse width between about 20-500 μs or about 100-400 μs, and a stimulation rate between about 1-20 Hz or about 15-20 Hz. In addition, the programmable controller may be programmed to direct the one or more electrodes to stimulate the tissue in a charge-balanced manner. Further, the programmable controller may be programmed to direct the one or more electrodes to stimulate the tissue with increasing pulse amplitudes to a peak pulse amplitude and then stimulate with decreasing pulse amplitudes. In one embodiment, the programmable controller is programmed to direct the one or more electrodes to stimulate the dorsal ramus nerve that innervates the multifidus muscle. The programmable controller also may be programmed to direct the one or more electrodes to stimulate the fascicles of the dorsal ramus nerve that innervates the multifidus muscle.

The first, second, and/or third communication circuits may be inductive and/or employ RF transceivers.

In one embodiment, the handheld activator includes a pad coupled to a handheld housing by a cable. Preferably, the cable has a sufficient length to enable a user to place the pad in extracorporeal proximity to the IPG while viewing the handheld housing.

In accordance with another aspect of the present invention, a method for restoring muscle function of the lumbar spine to reduce back pain is provided. The method includes providing one or more electrodes, an implantable pulse generator, an external programmer, and a handheld activator; implanting the one or more electrodes in or adjacent to tissue associated with control of the lumbar spine; implanting the implantable pulse generator in communication with the one or more electrodes; transferring programming data to the implantable pulse generator from the external programmer; and operating the handheld activator to command the implantable pulse generator to stimulate the tissue with the one or more electrodes responsive to the programming data.

V. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary embodiment of a stimulator system constructed in accordance with the principles of the present invention.

FIG. 2 shows an exemplary electrode lead of the stimulator system of FIG. 1.

FIG. 3A shows an exemplary implantable pulse generator (IPG) of the stimulator system of FIG. 1.

FIGS. 3B through 3D show alternative generalized block diagrams of the IPG of FIG. 3A, wherein the IPG of FIG. 3B has an inductive communications circuit, the IPG of FIG. 3C has a RF transceiver communications circuit, and the IPG of FIG. 3D has an inductive communications circuit and a RF transceiver communications circuit.

FIG. 4A shows an exemplary activator of the stimulator system of FIG. 1.

FIGS. 4B and 4C show alternative generalized block diagrams of the activator of FIG. 4A, wherein the activator of FIG. 4B has an inductive communications circuit and the activator of FIG. 4C has a RF transceiver communications circuit.

FIG. 5A shows an exemplary external programmer of the stimulator system of FIG. 1.

FIGS. 5B and 5C show alternative generalized block diagrams of the external programmer of FIG. 5A, wherein the external programmer of FIG. 5B has an inductive communications circuit and the external programmer of FIG. 5C has a RF transceiver communications circuit.

FIG. 6 is a block diagram of the functional components of an exemplary software-based programming system of the stimulator system of FIG. 1.

FIGS. 7A through 7D show an exemplary method for implanting an electrode lead and IPG in accordance with the principles of the present invention.

FIG. 8 shows a graph depicting an exemplary charge-balanced electrical stimulation waveform that may be delivered by the electrodes and IPG of the present invention.

FIG. 9 shows a graph depicting an exemplary stimulation pulse train that may be delivered by the electrodes and IPG of the present invention.

FIG. 10 shows a graph depicting an exemplary session that may be delivered by the electrodes and IPG of the present invention.

FIGS. 11-15 are exemplary screenshots illustrating various aspects of the user interface of the software-based programming system of the present invention.

VI. DETAILED DESCRIPTION OF THE INVENTION

The neuromuscular stimulation system of the present invention comprises implantable devices for facilitating electrical stimulation to tissue within a patient's back and external devices for wirelessly communicating programming data and stimulation commands to the implantable devices. The devices disclosed herein may be utilized to stimulate tissue associated with local segmental control of the lumbar spine in accordance with the programming data to rehabilitate the tissue over time. In accordance with the principles of the present invention, the stimulator system may be optimized for use in treating back pain of the lumbar spine.

Referring to FIG. 1, an overview of an exemplary stimulator system constructed in accordance with the principles of the present invention is provided. In FIG. 1, components of the system are not depicted to scale on either a relative or absolute basis. Stimulator system 100 includes electrode lead 200, implantable pulse generator (IPG) 300, activator 400, optional magnet 450, external programmer 500, and software-based programming system 600.

Electrode lead 200 includes lead body 202 having a plurality of electrodes, illustratively, electrodes 204, 206, 208, and 210. Electrode lead 200 is configured for implantation in or adjacent to tissue, e.g., nervous tissue, muscle, a ligament, and/or a joint capsule including tissue associated with local segmental control of the lumbar spine. Electrode lead 200 is coupled to IPG 300, for example, via connector block 302. IPG 300 is configured to generate pulses such that electrodes 204, 206, 208, and/or 210 deliver neuromuscular electrical stimulation (“NMES”) to target tissue. In one embodiment, the electrodes are positioned to stimulate a peripheral nerve where the nerve enters skeletal muscle, which may be one or more of the multifidus, transverse abdominus, quadratus lumborum, psoas major, internus abdominus, obliquus externus abdominus, and erector spinae muscles. Such stimulation may induce contraction of the muscle to restore neural control and rehabilitate the muscle, thereby improving muscle function of local segmental muscles of the lumbar spine, improving lumbar spine stability, and reducing back pain.

IPG 300 is controlled by, and optionally powered by, activator 400, which includes control module 402 coupled to pad 404, e.g., via cable 406. Control module 402 has user interface 408 that permits a user, e.g., patient, physician, caregiver, to adjust a limited number of operational parameters of IPG 300 including starting and stopping a treatment session. Control module 402 communicates with IPG 300 via pad 404, which may comprise an inductive coil or RF transceiver configured to communicate information in a bidirectional manner across a patient's skin to IPG 300 and, optionally, to transmit power to IPG 300.

Stimulator system 100 also may include optional magnet 450 configured to transmit a magnetic field across a patient's skin to IPG 300 such that a magnetic sensor of IPG 300 senses the magnetic field and IPG 300 starts or stops a treatment session responsive to the sensed magnetic field.

In FIG. 1, software-based programming system 600 is installed and runs on a conventional laptop computer, and is used by the patient's physician together with external programmer 500 to provide programming to IPG 300. During patient visits, external programmer 500 may be coupled, either wirelessly or using a cable such as cable 502, to the physician's computer such that software-based programming system 600 may download for review data stored on IPG 300 via external programmer 500. Software-based programming system 600 also may transfer programming data to IPG 300 via external programmer 500 to reprogram stimulation parameters programmed into IPG 300. For example, programming system 600 may be used to program and adjust parameters such as pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration. Programming system 600 also may be configured to upload and store data retrieved from IPG 300 to a remote server for later access by the physician.

Referring now to FIG. 2, an exemplary embodiment of electrode lead 200 is described. Electrode lead 200 contains a plurality of electrodes 204, 206, 208, and 210, disposed at distal end 210 of lead body 202, that are configured to be implanted in or adjacent to tissue, such as nervous tissue, muscle, ligament, and/or joint capsule. Lead body 202 is a suitable length for positioning the electrodes in or adjacent to target tissue while IPG is implanted in a suitable location, e.g., the lower back. For example, lead body 202 may be between about 30 and 80 cm in length, and preferably about 45 or about 65 cm in length. Lead body 202 is also of a suitable diameter for placement, for example, between about 1 and 2 mm in diameter and preferably about 1.3 mm. Electrodes 204, 206, 208, and 210 may be configured to stimulate the tissue at a stimulation frequency and at a level and duration sufficient to cause muscle to contract and may be ring electrodes, partial electrodes, segmented electrodes, nerve cuff electrodes placed around the nerve innervating the target muscle, or the like. Electrodes 204, 206, 208, 210 are a suitable length(s) and spaced apart a suitable distance along lead body 202. For example, electrodes 204, 206, 208, 210 may be about 2-5 mm in length, and preferably about 3 mm, and may be spaced apart about 2-6 mm, and preferably about 4 mm. As will also be understood by one of skill in the art, an electrode lead may contain more or fewer than four electrodes.

Also at distal end 210, first and second fixation elements 212 and 214 are coupled to lead body 202 via first and second fixation rings 216 and 218, respectively. First and second fixation elements 212 and 214 are configured to sandwich an anchor site, e.g., muscle, therebetween to secure electrode lead 200 at a target site without damaging the anchor site. First fixation elements 212 are angled distally relative to lead body 202, and resist motion in the first direction and prevent, in the case illustrated, insertion of the lead too far, as well as migration distally. Second fixation elements 214 are angled proximally relative to lead body 202 and penetrate through a tissue plane and deploy on the distal side of the tissue immediately adjacent to the target of stimulation. First fixation elements 212 are configured to resist motion in the opposite direction relative to second fixation elements 214. This combination prevents migration both proximally and distally, and also in rotation. In the illustrated embodiment, first fixation elements 212 are positioned between electrode 208 and distal most electrode 210 and second fixation element 214 is positioned between distal most electrode 210 and end cap 220. The length of and spacing between the fixation elements is defined by the structure around which they are to be placed. In one embodiment, the length of each fixation element is between about 1.5-4 mm and preferably about 2.5 mm and the spacing is between about 2 mm and 10 mm and preferably about 6 mm. First and second fixation elements 212 and 214 are configured to collapse inward toward lead body 202 in a delivery state and to expand, e.g., due to retraction of a sheath, in a deployed state. While FIG. 2 illustrates fixation elements 212 and 214 on lead body 202, it should be understood that other fixation elements may be used to anchor electrode lead 200 at a suitable location including the fixation elements described in U.S. Patent Application Pub. No. 2013/0131766 to Crosby and U.S. patent application Ser. No. 13/797,100, both assigned to the assignee of the present invention, the entire contents of each of which is incorporated herein by reference.

Lead body 202 further includes stylet lumen 222 extending therethrough. Stylet lumen 222 is shaped and sized to permit a stylet to be inserted therein, for example, during delivery of electrode lead 200. In one embodiment, end cap 220 is used to prevent the stylet from extending distally out of stylet lumen 222 beyond end cap 220.

At proximal end 224, electrode lead 200 includes contacts 226, 228, 230, and 232 separated along lead body 202 by spacers 234, 236, 238, 240, and 242. Contacts 226, 228, 230, and 232 may comprise an isodiametric terminal and are electrically coupled to electrodes 204, 206, 208, and 210, respectively, via, for example, individually coated spiral wound wires. A portion of proximal end 224 is configured to be inserted in IPG 300 and set-screw retainer 244 is configured to receive a screw from IPG 300 to secure the portion of electrode lead 200 within IPG 300.

As would be apparent to one of ordinary skill in the art, various electrode locations and configurations would be acceptable, including the possibility of skin surface electrodes. The electrode(s) may be an array of a plurality of electrodes, or may be a simple single electrode where the electrical circuit is completed with an electrode placed elsewhere (not shown) such as a skin surface patch or by the can of an implanted pulse generator. In addition, electrode lead 200 may comprise a wirelessly activated or leadless electrode, such as described in U.S. Pat. No. 8,321,021 to Kisker, such that no lead need be coupled to IPG 300.

Referring to FIG. 3A, IPG 300 is configured to generate pulses for electrical transmission to electrode lead 200. As is common with other active implantable medical devices, the IPG electronics are housed in a hermetically sealed metal housing 304. Housing 304 may comprise titanium or other biocompatible material, and includes connector block 302 that permits electrode lead 200 to be electrically coupled to the electronics within housing 304 via channel 306. Channel 306 is coupled to conductors 308, 310, 312, and 314 which are coupled to the IPG electronics. When proximal end 224 of electrode lead 200 is inserted within channel 306, conductors 308, 310, 312, and 314 are electrically coupled to contacts 226, 228, 230, and 232, respectively, and, in turn, electrically coupled to electrodes 204, 206, 208, and 210, respectively. Set-screw 316 is configured to be tightened down on set-screw retainer 244 to secure a portion of electrode lead 200 within channel 306. IPG 300 further includes a second channel (not shown) with four additional conductors. The two separate channels facilitate bilateral stimulation and the electrode configuration, e.g., combination of positive and negative electrodes, may be programmed independently for each channel.

As will be appreciated by one of ordinary skill in the art, while IPG 300 is illustratively implantable, a stimulator may be disposed external to a body of a patient on a temporary or permanent basis without departing from the scope of the present invention. For example, an external stimulator may be coupled to the electrodes wirelessly.

With respect to FIG. 3B, a generalized schematic diagram of the internal functional components of IPG 300 is now described. IPG 300 may include programmable controller 318, telemetry system 320 coupled to coil 322, power supply 324, electrode switching array 326, system sensors 328, and optional therapeutic circuitry module 330.

Controller 318 is electrically coupled to, and configured to control, the internal functional components of IPG 300. Controller 318 may comprise a commercially available microcontroller unit including a programmable microprocessor, volatile memory, nonvolatile memory such as EEPROM for storing programming, and nonvolatile storage, e.g., Flash memory, for storing firmware and a log of system operational parameters and patient data. The memory of controller 318 stores program instructions that, when executed by the processor of controller 318, cause the processor and the functional components of IPG 300 to provide the functionality ascribed to them herein. Controller 318 is configured to be programmable such that programming data is stored in the memory of controller 318 and may be adjusted using external programmer 500 as described below. Programming data may include pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration. In accordance with one embodiment, programmable parameters, their ranges, and nominal values are:

Parameter Min Max Nominal Amplitude 0 mA 7.0 mA 1 mA Pulse Width 25 μs 500 μs 200 μs Rate 1 Hz 40 Hz 20 Hz On Ramp 0 s 5 s 2 s Off Ramp Cycle-On 2 s 20 s 10 s Cycle-Off 20 s 120 s 20 s Session 1 min 60 min 30 min

Controller 318 may be programmable to allow electrical stimulation between any chosen combination of electrodes on the lead, thus providing a simple bipolar configuration. In addition, controller 318 may be programmed to deliver stimulation pulses in a guarded bipolar configuration (more than 1 anode surrounding a central cathode) or IPG housing 304 may be programmed as the anode, enabling unipolar stimulation from any of the electrodes.

Controller 318 further may be programmed with a routine to calculate the impedance at electrode lead 200. For example, controller 318 may direct power supply 324 to send an electrical signal to one or more electrodes which emit electrical power. One or more other electrodes receive the emitted electrical power and send a received signal to controller 318 that runs the routine to calculate impedance based on the sent signal and the received signal.

Controller 318 is coupled to communications circuitry including telemetry system 320, which is electrically coupled to coil 322, that permits transmission of stimulation commands, and optionally power, between IPG 300 and activator 400 such that IPG 300 may be powered, programmed, and/or controlled by activator 400. For example, controller 318 may start or stop a treatment session responsive to stimulation commands received from a corresponding telemetry system and coil of activator 400 via coil 322 and telemetry system 320. Telemetry system 320 and coil 322 further permit transmission of programming data, and optionally power, between IPG 300 and external programmer 500 such that IPG 300 may be powered, programmed, and/or controlled by software-based programming system 600 via external programmer 500. For example, controller 318 may direct changes to at least one of pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration responsive to programming data received from a corresponding telemetry system and coil of external programmer 500 via coil 322 and telemetry system 320.

The technology for telemetry system 320 and coil 322 is well known to one skilled in the art and may include a magnet, a short range telemetry system, a longer range telemetry system (such as using MICS RF Telemetry available from Zarlink Semiconductor of Ottawa, Canada), or technology similar to a pacemaker programmer. Alternatively, coil 322 may be used to transmit power only, and separate radio frequency transmitters may be provided in IPG 300 activator 400, and/or external programmer 500 for establishing bidirectional or unidirectional data communication.

Power supply 324 powers the electrical components of IPG 300, and may comprise a primary cell or battery, a secondary (rechargeable) cell or battery or a combination of both. Alternatively, power supply 324 may not include a cell or battery, but instead comprise a capacitor that stores energy transmitted through the skin via a Transcutaneous Energy Transmission System (TETs), e.g., by inductive coupling. In a preferred embodiment, power supply 324 comprises a lithium ion battery.

Controller 318 further may be coupled to electrode switching array 326 so that any subset of electrodes of the electrode leads may be selectably coupled to therapeutic circuitry module 330, described in detail below. In this way, an appropriate electrode set may be chosen from the entire selection of electrodes implanted in the patient's body to achieve a desired therapeutic effect. Electrode switching array 326 preferably operates at high speed, thereby allowing successive stimulation pulses to be applied to different electrode combinations.

System sensors 328 may comprise one or more sensors that monitor operation of the systems of IPG 300, and log data relating to system operation as well as system faults, which may be stored in a log for later readout using software-based programming system 600. In one embodiment, system sensors 328 include a magnetic sensor configured to sense a magnetic field and to transmit a signal to controller 318 based on the sensed magnetic field such that the controller starts or stops a treatment session. In another embodiment, system sensors 328 include one or more sensors configured to sense muscle contraction and to generate a sensor signal based on the muscle contraction. Controller 318 is configured to receive the sensor signal from system sensors 328 and to adjust the stimulation parameters based on the sensor signal. In one embodiment, system sensors 328 sense an increase or decrease in muscle movement and controller 318 increases or decreases the stimulation frequency to maintain smooth and continuous muscle contraction.

In one embodiment, sensors 328 may include an accelerometer that senses acceleration of a muscle caused by muscle contraction. The accelerometer may be a 1-, 2- or 3-axis analog or digital accelerometer that determines whether the patient is active or asleep or senses overall activity of the patient, which may be a surrogate measure for clinical parameters (e.g., more activity implies less pain), and/or a heart rate or breathing rate (minute ventilation) monitor, e.g., which may be obtained using one or more of the electrodes disposed on the electrode leads. The accelerometer may be used to determine the orientation of IPG 300, and by inference the orientation of the patient, at any time. For example, after implantation, software-based programming system 600 may be used to take a reading from the implant, e.g., when the patient is lying prone, to calibrate the orientation of the accelerometer. If the patient is instructed to lie prone during therapy delivery, then the accelerometer may be programmed to record the orientation of the patient during stimulation, thus providing information on patient compliance. In other embodiments, system sensors 328 may include a pressure sensor, a movement sensor, and/or a strain gauge configured to sense muscle contraction and to generate a sensor signal based on the muscle contraction, and in a further embodiment, various combinations of at least one of an accelerometer, a pressure sensor, a movement sensor, and/or a strain gauge are included.

Sensors 328 may also include, for example, a humidity sensor to measure moisture within housing 304, which may provide information relating to the state of the electronic components, or a temperature sensor, e.g., for measuring battery temperature during charging to ensure safe operation of the battery. Data from the system sensors may be logged by controller 318 and stored in nonvolatile memory for later transmission to software-based programming system 600 via external programmer 500.

As will be appreciated by one of ordinary skill in the art, system sensors 328 may be placed in a variety of locations including within housing 302, within or adjacent to the tissue that is stimulated, and/or in proximity to the muscle to be contracted and connected via a separate lead to IPG 300. In other embodiments, sensors 324 may be integrated into one or more of the leads used for stimulation or may be an independent sensor(s) operatively coupled to IPG 300 using, for example, radio frequency (RF) signals for transmitting and receiving data.

Controller 318 also may be coupled to optional therapeutic circuitry module 330 that provides any of a number of complimentary therapeutic stimulation, analgesic, feedback or ablation treatment modalities as described in detail below. IPG 300 illustratively includes one therapeutic circuitry module 330, although additional circuitry modules may be employed in a particular embodiment depending upon its intended application, as described in U.S. Patent Application Publication No. 2011/0224665 to Crosby, assigned to the assignee of the present invention, the entire contents of which is incorporated herein by reference. Therapeutic circuitry module 330 may be configured to provide different types of stimulation, either to induce muscle contractions or to block pain signals in afferent nerve fibers; to monitor muscle contractions induced by stimulation and adjust the applied stimulation regime as needed to obtain a desired result; or to selectively and intermittently ablate nerve fibers to control pain and thereby facilitate muscle rehabilitation.

Referring to FIG. 3C, IPG 300′ is constructed similarly to IPG 300 of FIG. 3B, wherein like components are identified by like-primed reference numbers. Thus, for example, power supply 324′ in FIG. 3C corresponds to power supply 324 of FIG. 3B, etc. As will be observed by comparing FIGS. 3B and 3C, IPG 300′ includes a communications circuit employing transceiver 332 coupled to antenna 334 (which may be inside or external to the hermetic housing) rather than telemetry system 320 and coil 322 of IPG 300.

Transceiver 332 preferably comprises a radio frequency (RF) transceiver and is configured for bi-directional communications via antenna 334 with a similar transceiver circuit disposed in activator 400 and/or external programmer 500. For example, transceiver 332 may receive stimulation commands from activator 400 and programming data from software-based programming system 600 via external programmer 500. Controller 318 may direct changes to at least one of pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration, including commands to start or stop a treatment session, responsive to programming data and/or stimulation commands received from a corresponding transceiver and antenna of activator 400 and/or external programmer 500 via antenna 334 and transceiver 332. Transceiver 332 also may include a low power mode of operation, such that it periodically awakens to listen for incoming messages and responds only to those messages including the unique device identifier assigned to that IPG. In addition, transceiver 332 may employ an encryption routine to ensure that messages sent from, or received by, IPG 300 cannot be intercepted or forged.

Referring to FIG. 3D, IPG 300″ is constructed similarly to IPG 300 of FIG. 3B and IPG 300′ of FIG. 3C except that IPG 300″ includes a communications circuit employing telemetry system 320″ and coil 322″ and a communications circuit employing transceiver 332″ and antenna 334″. IPG 300″ is preferably in an embodiment where IPG 300″ communicates inductively and using RF. In one embodiment, telemetry system 320″ and coil 322″ are configured to transfer stimulation commands, and optionally power, between IPG 300″ and activator 400 from a corresponding telemetry system and coil of activator 400. In such an embodiment, transceiver 332″ and antenna 334″ are configured to transfer programming data between IPG 300″ and external programmer 500′ from a corresponding transceiver and antenna of external programmer 500′. In an alternative embodiment, telemetry system 320″ and coil 322″ permit transfer of programming data, and optionally power, between IPG 300″ and external programmer 500 from a corresponding telemetry system and coil of external programmer 500. In such an embodiment, transceiver 332″ and antenna 334″ are configured for transfer of stimulation commands between IPG 300″ and activator 400′ from a corresponding transceiver and antenna of activator 400′.

Referring now to FIG. 4A, exemplary activator 400, including control module 402 and pad 404, is described. Control module 402 includes housing 410 sized for handheld use and user interface 408. User interface 408 permits a user, e.g., patient, physician, caregiver, to adjust a limited number of operational parameters of IPG 300 including starting and stopping a treatment session. Illustratively, user interface 408 includes signal LED 412, status LED 414, warning LED 416, start button 418, stop button 420, status button 422, and battery LED 424. Signal LED 412 preferably contains multiple diodes, each of which emit light of a different preselected color. Signal LED 412 is configured to illuminate when the communications circuit within pad 404 detects a suitable connection with a the corresponding communications circuit in IPG 300 suitable for power transmission and/or data communication between IPG 300 and activator 400. In one embodiment, signal LED 412 illuminates a red diode when there is not a suitable connection, a yellow diode when the connection is suitable but weak, and a green diode when the connection is suitable and strong. Status LED 414 also may include multiple diodes that illuminate in a pattern of flashes and/or colors to indicate to the user the status of IPG 300. Such patterns are stored in the memory of the controller of control module 402 and may indicate whether the IPG is directing stimulation to occur or awaiting commands. A user may refer to a user manual to decode a pattern shown on status LED 414. Warning LED 416 is configured to illuminate when the controller of control module 402 detects an error and indicates that a user should contact their physician or clinic. When start button 418 is pressed, the controller of control module 402 directs a signal to be sent to IPG 300 via pad 404 and cable 406 to begin a treatment session. When stop button 420 is pressed, the controller of control module 402 directs a signal to be sent to IPG 300 via pad 404 and cable 406 to end a treatment session. Alternatively, the treatment session may have a predetermined length and the controller de-energizes the electrodes when the session time expires. Battery LED 424 is configured to illuminate when the controller in control module 402 detects that the battery levels are below a predetermined threshold.

Pad 404 is configured to communicate information and, optionally, transfer power from control module 402 to IPG 300 in a bidirectional manner across a patient's skin. In one embodiment, pad 404 includes an inductive coil within its housing. Cable 406 is a suitable length so that a patient may comfortably place pad 404 in extracorporeal proximity to IPG 300 implanted in the patient's lower back while viewing control module 402 to confirm correct placement using signal LED 412.

With respect to FIG. 4B, a generalized schematic diagram of the internal functional components of activator 400 is now described. Activator 400 may include programmable controller 426, telemetry system 428 coupled to coil 430, user interface 432, power supply 434, and input and output circuitry (I/O) 436. In a preferred embodiment, programmable controller 426, telemetry system 428, user interface 432, power supply 434, and input and output circuitry (I/O) 436 are housed within control module housing 410 and coil 430 is housed within the housing for pad 404.

Controller 426 is electrically coupled to, and configured to control, the internal functional components of activator 400. Controller 426 may comprise a commercially available microcontroller unit including a programmable microprocessor, volatile memory, nonvolatile memory such as EEPROM for storing programming, and nonvolatile storage, e.g., Flash memory, for storing firmware and a log of system operational parameters and patient data. The memory of controller 426 may store program instructions that, when executed by the processor of controller 426, cause the processor and the functional components of activator 400 to provide the functionality ascribed to them herein. Controller 426 is configured to be programmable. For example, controller 426 may send stimulation commands responsive to user input received at user interface 432 to controller 318 of IPG 300 via the telemetry (or RF) systems to start or stop a treatment session. In a preferred embodiment, a limited number of stimulation parameters may be adjusted at user interface 432 to minimize the chance of injury caused by adjustments made by non-physician users. In an alternative embodiment, controller 426 also may send adjustments to stimulation parameters, e.g., pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration to IPG 300 responsive to user input received at user interface 432.

Controller 426 is coupled to telemetry system 428, which is electrically coupled to coil 430 (e.g., via cable 406), that permits transmission of energy and stimulation commands between activator 400 and IPG 300 (or IPG 300″) such that IPG 300 may be powered, programmed, and/or controlled by activator 400 responsive to user input received at user interface 432. For example, controller 426 may direct telemetry system 428 and coil 430 to send adjustments to stimulation parameter(s), including commands to start or stop a treatment session or provide status of the IPG, responsive to user input received at user interface 432 to coil 322 and telemetry system 320 of IPG 300. The technology for telemetry system 428 and coil 430 is well known to one skilled in the art and may be similar to telemetry system 320 and coil 322 described above. Alternatively, coil 430 may be used to transmit power only, and separate radio frequency transmitters may be provided in activator 400 and IPG 300 for establishing bidirectional or unidirectional data communication.

User interface 432 is configured to receive user input and to display information to the user. As described above, user interface 432 may include buttons for receiving user input and LEDs for displaying information to the user. As will be readily apparent to one skilled in the art, user interface 432 is not limited thereto and may use a display, a touch screen, a keypad, a microphone, a speaker, a trackball, or the like.

Power supply 434 powers the electrical components of activator 400, and may comprise a primary cell or battery, a secondary (rechargeable) cell or battery or a combination of both. Alternatively, power supply 434 may be a port to allow activator 400 to be plugged into a conventional wall socket for powering components.

Input and output circuitry (I/O) 436 may include ports for data communication such as wired communication with a computer and/or ports for receiving removable memory, e.g., SD card, upon which program instructions or data related to activator 400 use may be stored.

Referring to FIG. 4C, activator 400′ is constructed similarly to activator 400 of FIG. 4B except that activator 400′ includes a communications circuit employing transceiver 438 and antenna 440 rather than a communications circuit employing telemetry system 428 and coil 430. Transceiver 438 preferably comprises a radio frequency (RF) transceiver and is configured for bi-directional communications via antenna 440 with transceiver 332 via antenna 334 of IPG 300′. Transceiver 438 may transmit stimulation commands from activator 400′ to IPG 300′ (or IPG 300″). For example, controller 426′ may direct transceiver 438 to transmit commands to start or stop a treatment session to IPG 300′ responsive to user input received at user interface 432′. In one embodiment, controller 426′ may direct transceiver 438 to transmit a command to provide status of IPG 300′ or commands to adjust stimulation parameter(s) to IPG 300′ responsive to user input received at user interface 432′.

Transceiver 438 also may include a low power mode of operation, such that it periodically awakens to listen for incoming messages and responds only to those messages including the unique device identifier assigned to that activator. In addition, transceiver 438 may employ an encryption routine to ensure that messages sent from, or received by, activator 400′ cannot be intercepted or forged.

Referring now to FIG. 5A, exemplary external programmer 500 is now described. External programmer 500 includes housing 504 sized for handheld use and user interface 506. User interface 506 permits a user, e.g., patient, physician, caregiver, to send programming data to IPG 300 including commands to adjust stimulation parameters. Illustratively, user interface 506 includes status LED 508, status button 510, and signal LEDs 512. Status LED 508 is configured to illuminate when status button 510 is pressed to indicate a successful communication has been sent to IPG 300, e.g., command to stop a treatment session. Signal LEDs 512 are configured to illuminate based on the strength of the signal between IPG 300 and external programmer 500. The controller of external programmer 500 may direct appropriate signal LEDs 512 to illuminate based on the strength of the signals between the respective telemetry systems and coils or transceivers and antennas of external programmer 500 and IPG 300. Signal LEDs 512 may include diodes with different colors. For example, signal LEDs 512 may include red diodes configured to illuminate when the signal strength between external programmer 500 and IPG 300 is weak or non-existent, yellow diodes configured to illuminate when the signal strength between external programmer 500 and IPG 300 is medium, and green diodes configured to illuminate when the signal strength between external programmer 500 and IPG 300 is strong. External programmer 500 further includes port 514 configured to receive cable 502 such that external programmer 500 is electrically coupled and may communicate programming data with software-based programming system 600 run on a computer.

With respect to FIG. 5B, a generalized schematic diagram of the internal functional components of external programmer 500 is now described. External programmer 500 may include programmable controller 516, telemetry system 518 coupled to coil 520, user interface 522, power supply 524, and input and output circuitry (I/O) 526.

Controller 516 is electrically coupled to, and configured to control, the internal functional components of external programmer 500. Controller 516 may comprise a commercially available microcontroller unit including a programmable microprocessor, volatile memory, nonvolatile memory such as EEPROM for storing programming, and nonvolatile storage, e.g., Flash memory, for storing firmware and a log of system operational parameters and patient data. The memory of controller 516 may store program instructions that, when executed by the processor of controller 516, cause the processor and the functional components of external programmer 500 to provide the functionality ascribed to them herein. Controller 516 is configured to be programmable such that stimulation parameters, e.g., pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration may be adjusted responsive to user input received at user interface 522. For example, controller 516 may send programming data responsive to user input received at user interface 522 to controller 318 of IPG 300 via the respective telemetry (or RF) systems to adjust stimulation parameters or to start or stop a treatment session. In a preferred embodiment, only a physician has access to external programmer 500 to minimize the chance of injury caused by adjustments made by non-physician users.

Controller 516 is coupled to telemetry system 518, which is electrically coupled to coil 520, that permits transmission of programming data, and optionally power, between software-based programming system 600 and IPG 300 (or IPG 300″) via external programmer 500. In this manner, IPG 300 may be powered, programmed, and/or controlled by software-based programming system 600 and external programmer 500 responsive to user input received at user interface 522. For example, controller 516 may direct telemetry system 518 to transmit stimulation parameter(s) such as pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration, including commands to start or stop a treatment session, to IPG 300 responsive to user input received at user interface 522 and/or software-based programming system 600. As another example, controller 516 may direct telemetry system 518 to transmit interrogation commands such as requests for the actual value of stimulation parameter(s), battery voltage, data logged at IPG 300, and IPG 300 status data, to IPG 300 responsive to user input received at user interface 522 and/or software-based programming system 600, and to receive responses to the interrogation commands from IPG 300. As yet another example, controller 516 may direct telemetry system 518 to transmit commands to IPG 300 to calculate the impedance of electrode lead 200 using a routine stored on controller 318 of IPG 300 and to receive the calculated lead impedance from the telemetry system of IPG 300. The technology for telemetry system 518 and coil 520 is well known to one skilled in the art and may be similar to telemetry system 320 and coil 322 described above. Alternatively, coil 520 may be used to transmit power only, and separate radio frequency transmitters may be provided in external programmer 500 and IPG 300 for establishing directional data communication.

User interface 522 is configured to receive user input and to display information to the user. As described above, user interface 522 may include buttons for receiving user input and LEDs for displaying information to the user. As will be readily apparent to one skilled in the art, user interface 522 is not limited thereto and may use a display, a touch screen, a keypad, a microphone, a speaker, a trackball, or the like.

Power supply 524 powers the electrical components of external programmer 500, and may comprise a primary cell or battery, a secondary (rechargeable) cell or battery or a combination of both. Alternatively, power supply 524 may be a port to allow external programmer 524 to be plugged into a conventional wall socket for powering components. In one preferred embodiment, power supply 524 comprises a USB port and cable that enables external programmer 500 to be powered from a computer, e.g., via cable 502, running software-based programming system 600.

Input and output circuitry (I/O) 526 may include ports for data communication such as wired communication with a computer and/or ports for receiving removable memory, e.g., SD card, upon which program instructions or data related to external programmer 500 use may be stored. In one embodiment, I/O 526 comprises port 514, and corresponding circuitry, for accepting cable 502 such that external programmer 500 is electrically coupled to a computer running software-based programming system 600.

Referring to FIG. 5C, external programmer 500′ is constructed similarly to external programmer 500 of FIG. 5B except that external programmer 500′ includes a communications circuit employing transceiver 528 and antenna 530 rather than a communications circuit employing telemetry system 518 and coil 520. Transceiver 528 preferably comprises a radio frequency (RF) transceiver and is configured for bi-directional communications via antenna 530 with transceiver 332 via antenna 334 of IPG 300′. Transceiver 528 may transmit programming data from external programmer 500′ to IPG 300′ (or IPG 300″). For example, controller 516′ may direct transceiver 528 to transmit stimulation parameter(s) such as pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration, including commands to start or stop a treatment session, to IPG 300′ responsive to user input received at user interface 522′ and/or software-based programming system 600. As another example, controller 516′ may direct transceiver 528 to transmit interrogation commands such as requests for the actual value of stimulation parameter(s), battery voltage, data logged at IPG 300′, and IPG 300′ status data, to IPG 300′ responsive to user input received at user interface 522′ and/or software-based programming system 600, and to receive responses to the interrogation commands from IPG 300′. As yet another example, controller 516′ may direct transceiver 528 to transmit commands to IPG 300′ to calculate the impedance of electrode lead 200 using a routine stored on controller 318′ of IPG 300′ and to receive the calculated lead impedance from transceiver 332 of IPG 300′.

Transceiver 528 also may include a low power mode of operation, such that it periodically awakens to listen for incoming messages and responds only to those messages including the unique device identifier assigned to that external programmer. In addition, transceiver 528 may employ an encryption routine to ensure that messages sent from, or received by, external programmer 500′ cannot be intercepted or forged.

Referring now to FIG. 6, the software implementing programming system 600 is now described. The software of programming system 600 comprises a number of functional blocks, schematically depicted in FIG. 6, including main block 602, event logging block 604, data download block 606, configuration setup block 608, user interface block 610, alarm detection block 612, sensor calibration block 614, firmware upgrade block 616, device identifier block 618, and status information block 620. The software preferably is written in C++ and employs an object oriented format. In one preferred embodiment, the software is configured to run on top of a Microsoft Windows™ (a registered trademark of Microsoft Corporation, Redmond, Wash.) or Unix-based operating system, such as are conventionally employed on desktop and laptop computers. The computer running programming system 600 preferably includes a data port, e.g., USB port or comparable wireless connection, that permits external programmer 500 and/or activator 400 to be coupled thereto. Alternatively, as discussed above, the computer may include a wireless card, e.g., conforming to the IEEE 802.11 standard, thereby enabling IPG 300, activator 400, and/or external programmer 500 to communicate wirelessly with the computer running programming system 600. As a further alternative, IPG 300, activator 400, and/or external programmer 500 may include a communications circuit(s) having telephony circuitry, e.g., GSM, CDMA, LTE circuitry, or the like, that automatically dials and uploads data, such as alarm data, from IPG 300 to a secure website accessible by the patient's physician.

Main block 602 preferably includes a main software routine that executes on the physician's computer, and controls overall operation of the other functional blocks. Main block 602 enables the physician to download event data and alarm information stored on IPG 300, via external programmer 500, to his office computer, and also permits programming system 600 to directly control operation of IPG 300, via external programmer 500. Main block also enables the physician to upload firmware updates and configuration data to IPG 300 via external programmer 500.

Event Log block 604 is a record of operational data downloaded from IPG 300, using external programmer 500, and may include, for example, treatment session start and stop times, current stimulation parameters, stimulation parameters from previous treatment sessions, sensor data, lead impedance, battery current, battery voltage, battery status, and the like. The event log also may include the occurrence of events, such as alarms or other abnormal conditions.

Data Download block 606 is a routine that commands IPG 300, using external programmer 500, to transfer data to programming system 600 for download after IPG 300 is coupled to the computer programming system 600 via external programmer 500. Data Download block 606 may initiate, either automatically or at the instigation of the physician via user interface block 610, downloading of data stored in the event log.

Configuration Setup block 608 is a routine that configures the parameters stored within IPG 300, using external programmer 500, that control operation of IPG 300. The interval timing parameters may determine, e.g., how long the processor remains in sleep mode prior to being awakened to listen for radio communications or to control IPG 300 operation. The interval timing parameters may control, for example, the duration of a treatment session. Interval timing settings transmitted to IPG 300 from programming system 600 also may determine when and how often event data is written to the memory in controller 318. In an embodiment in which external programmer 500 is also configured to transfer data to activator 400, programming system 600 also may be used to configure timing parameters used by the firmware executed by controller 426 of activator 400. Block 608 also may be used by the physician to configure parameters stored within the memory of controller 318 relating to limit values on operation of controller 318. These values may include times when IPG 300 may and may not operate, etc. Block 608 also may configure parameters store within the memory of controller 318 relating to control of operation of IPG 300. These values may include target numbers of treatment sessions and stimulation parameters.

User interface block 610 handles display of information retrieved from the programming system 600 and IPG 300, via external programmer 500, and data download block 606, and presents that information in an intuitive, easily understood format for physician review. Such information may include status of IPG 300, treatment session start and stop times, current stimulation parameters, stimulation parameters from previous treatment sessions, sensor data, lead impedance, battery status, and the like. User interface block 610 also generates user interface screens that permit the physician to input information to configure the session timing, stimulation parameters, requests to calculate lead impedance, etc.

Alarm detection block 612 may include a routine for evaluating the data retrieved from IPG 300, using external programmer 500, and flagging abnormal conditions for the physician's attention. For example, alarm detection block 612 may flag when a parameter measured by system sensors 328 is above or below a predetermined threshold.

Sensor calibration block 614 may include a routines for testing or measuring drift, of system sensors 328 employed in IPG 300, e.g., due to aging or change in humidity. Block 614 may then compute offset values for correcting measured data from the sensors, and transmit that information to IPG 300 for storage in the nonvolatile memory of controller 318.

Firmware upgrade block 616 may comprise a routine for checking the version numbers of the controller firmware installed on IPG 300, using external programmer 500, and identify whether upgraded firmware exists. If so, the routine may notify the physician and permit the physician to download revised firmware to IPG 300, in nonvolatile memory.

Device identifier block 618 consists of a unique identifier for IPG 300 that is stored in the nonvolatile memory of controller 318 and a routine for reading that data when programming system 600 is coupled to IPG 300 via external programmer 500. The device identifier also may be used by IPG 300 to confirm that wireless communications received from activator 400 and/or external programmer 500 are intended for that specific IPG. Likewise, this information is employed by activator 400 and/or external programmer 500 to determine whether a received message was generated by the IPG associated with that system. Finally, the device identifier information may be employed by programming system 600 to confirm that activator 400 and IPG constitute a matched set.

Status information block 620 comprises a routine for interrogating IPG 300, when connected via activator 400, or external programmer 500 and programming system 600, to retrieve current status data from IPG 300, using external programmer 500. Such information may include, for example, battery status, stimulation parameters, lead impedance, the date and time on the internal clocks of treatment sessions, version control information for the firmware and hardware currently in use, and sensor data.

Referring now to FIGS. 7A to 7D, an exemplary method for implanting an electrode lead and IPG is described. First, electrode lead 200, IPG 300, stylet (now shown), suture sleeve 700, introducer 702, and dilator 704 are provided, as shown in FIG. 7A. In FIG. 7A, components of the system are not depicted to scale on either a relative or absolute basis. Suture sleeve 700 illustratively includes first end section 706, middle section 708 separated from first end section by first groove 710, second end section 712 separated from middle section 708 by second groove 714, and sleeve lumen 716. First and second end sections 706 and 712 may have truncated conical portions as shown. First and second grooves 710 and 714 are sized and shaped to accept sutures such that suture sleeve 700 may be secured to tissue, e.g., superficial fascia, using the sutures. Sleeve lumen 716 is sized such that electrode lead 200 may be inserted therethrough.

Introducer 702 may include introducer lumen 718, distal tip 720, and coupling portion 722. Introducer lumen 718 extends through introducer 702 and is shaped and sized to permit electrode lead 200 to slide therethrough. Distal tip 720 is beveled to ease introduction through tissue. Coupling portion 722, illustratively a female end with threads, is configured to be coupled to a portion of dilator 704. In one embodiment, introducer 702 comprises a commercially available 7 French (Fr) introducer.

Dilator 704 may include dilator lumen 724, distal tip 726, coupling portion 728, and handle 730. Dilator lumen 724 extends through dilator 704 and is shaped and sized to permit introducer 702 to slide therethrough. Distal tip 726 is beveled to ease introduction through tissue. Coupling portion 728, illustratively a male end with threads, is configured to be coupled to a portion of introducer 702, e.g., coupling portion 722. Handle 730 is sized and shaped to permit a physician to comfortably hold dilator 704.

Next, a stylet is inserted within the stylet lumen of electrode lead 200 to provide additional stiffness to electrode lead 200 to ease passage of electrode lead 200 through introducer 702. The stylet may be a commercially available stylet such as a locking stylet available from Cook Group Incorporated of Bloomington, Ind. Electrode lead 200 then is inserted within introducer lumen 718 of introducer 702.

Using fluoroscopy, acoustic, anatomic, or CT guidance, dilator 704 is delivered transcutaneously and transmuscularly to a target site, e.g., in or adjacent to tissue associated with control of the lumbar spine. Such tissue may include nervous tissue, muscle, ligament, and/or joint capsule. In one embodiment, muscle includes skeletal muscle such as the multifidus, transverse abdominus, quadratus lumborum, psoas major, internus abdominus, obliquus externus abdominus, and erector spinae muscles and nervous tissue includes a peripheral nerve that innervates skeletal muscle. In a preferred embodiment, nervous tissue comprises the dorsal ramus nerve, or fascicles thereof, that innervate the multifidus muscle.

Next, introducer 702 (having a portion of the electrode lead disposed therein) is inserted through dilator lumen 724 to the target site. Introducer 702 may then be coupled to dilator 704, e.g., by screwing coupling portion 722 onto coupling portion 728.

FIGS. 7B-7D depict a lateral projection of a segment of a typical human lumbar spine shown having a vertebral body V, transverse process TP, inter-transverse ligament ITL, and a dorsal ramus DR. In FIG. 7B, dilator 704 having introducer 702 disposed therethrough, which has a portion of the electrode lead disposed therein, are positioned adjacent to the target site, illustratively, the medial branch of the dorsal ramus DR nerve that innervates the multifidus muscle. In one embodiment, electrodes of the electrode lead are positioned to stimulate the medial branch of the dorsal ramus that exits between the L2 and L3 lumbar segments and passes over the transverse process of the L3 vertebra, thereby eliciting contraction of fascicles of the lumbar multifidus at the L3, L4, L5 and S1 segments and in some patients also at the L2 segment.

Introducer 702 and dilator 704 are moved proximally, e.g., using handle 730, while maintaining the position of electrode lead 200 at the target site, as shown in FIG. 7C. The first and second fixation elements of electrode lead 200 individually transition from a collapsed state within introducer 702 to an expanded state, shown in FIG. 7C, as introducer 702 passes over the respective fixation element. The first and second fixation elements sandwich an anchor site, e.g., muscle, therebetween without damaging the anchor site in the expanded state to fix electrode lead 200 at the target site.

Introducer 702 and dilator 704 are moved proximally off the proximal end of electrode lead 200 and suture sleeve 700 is placed over the proximal end of electrode lead 200 and moved distally, as illustrated in FIG. 7D. When suture sleeve 700 is positioned adjacent to the superficial fascia SF beneath skin SK, sutures are sewn into the first and second grooves of suture sleeve 700 so as to secure suture sleeve 700 to the superficial fascia SF.

Finally, the IPG is coupled to the proximal end of electrode lead 200 and implanted within the lower back of the patient.

Exemplary stimulation parameters in accordance with aspects of the present invention are now described. Preferably, such stimulation parameters are selected and programmed to induce contraction of muscle to restore neural control and rehabilitate muscle associated with control of the spine, thereby improving lumbar spine stability and reducing back pain. As used in this specification, “to restore muscle function” means to restore an observable degree of muscle function as recognized by existing measures of patient assessment, such as the Oswestry Disability Index (“ODI”) as described in Lauridsen et al., Responsiveness and minimal clinically important difference for pain and disability instruments in low back pain patients, BMC Musculoskeletal Disorders, 7: 82-97 (2006), the European Quality of Life Assessment 5D (“EQ-5D”) as described in Brazier et al., A comparison of the EQ-5D and SF-6D across seven patient groups, Health Econ. 13: 873-884 (2004), or a Visual Analogue Scale (“VAS”) as described in Hagg et al., The clinical importance of changes in outcome scores after treatment for chronic low back pain, Eur Spine J 12: 12-20 (2003). In accordance with one aspect of the present invention, “to restore muscle function” means to observe at least a 15% improvement in one of the foregoing assessment scores within 30-60 days of initiation of treatment. As described above, the stimulation parameters may be programmed into the IPG, may be adjusted in the IPG responsive to (i) stimulation commands transferred from the activator or (ii) programming data transferred from the external programmer.

The stimulation parameters include, for example, pulse amplitude (voltage or current), pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, and electrode configuration, including commands to start or stop a treatment session. In one embodiment, pulse amplitude is programmed to be adjustable between 0 and 7 mA. In a preferred embodiment, pulse amplitude is programmed to be between about 2-5 mA, 2.5-4.5 mA, or 3-4 mA, and preferably about 3.5 mA. In one embodiment, pulse width is programmed to be adjustable between 25 and 500 μs. In a preferred embodiment, pulse width is programmed to be between about 100-400 μs, 150-350 μs, or 200-300 μs, and preferably about 350 μs. In one embodiment, stimulation rate is programmed to be adjustable between 1 and 40 Hz. In a preferred embodiment, stimulation rate is programmed to be between about 5-35 Hz, 10-30 Hz, or 15-20 Hz, and preferably about 20 Hz. In one embodiment, on ramp timing is programmed to be adjustable between 0 and 5 s. In a preferred embodiment, on ramp timing is programmed to be between about 0.5-4.5 s, 1-4 s, 1.5-3.5 s, or 2-3 s, and preferably about 2.5 s. In one embodiment, off ramp timing is programmed to be adjustable between 0 and 5 s. In a preferred embodiment, off ramp timing is programmed to be between about 0.5-4.5 s, 1-4 s, 1.5-3.5 s, or 2-3 s, and preferably about 2.5 s. In one embodiment, cycle-on timing is programmed to be adjustable between 2 and 20 s. In a preferred embodiment, cycle-on timing is programmed to be between about 4-18 s, 6-16 s, 8-14 s, 9-13 s, or 10-12 s and preferably about 10 s. In one embodiment, cycle-off timing is programmed to be adjustable between 20 and 120 s. In a preferred embodiment, cycle-off timing is programmed to be between about 30-110 s, 40-100 s, 50-90 s, 55-85 s, 60-80 s, or 65-75 s and preferably about 70 s. In one embodiment, session timing is programmed to be adjustable between 1 and 60 min. In a preferred embodiment, session timing is programmed to be between about 5-55 min, 10-50 min, 15-45 min, 20-40 min, or 25-35 min, and preferably about 30 min.

FIG. 8 is a graph of an exemplary charge-balanced electrical stimulation waveform that may be delivered by the electrodes and IPG of the present invention. The IPG directs the electrodes, responsive to programming, stimulation commands, and/or received programming data, to stimulate at a pulse amplitude for the time of a pulse width and then balances the charge by dropping to a negative pulse amplitude and then bringing the pulse amplitude back to zero over the time of a waveform. The stimulation may be current-controlled and charge-balanced, or voltage-controlled and charge-balanced.

FIG. 9 is a graph showing an exemplary stimulation pulse train that may be delivered by the electrodes and IPG of the present invention. During cycle-on programming, the IPG directs the electrodes, responsive to programming, stimulation commands, and/or received programming data, to deliver a stimulation pulse train in an “on ramp” manner such that the pulse amplitude increases in predetermined increments to reach the programmed peak pulse amplitude. In this way, the number of pulses in the “on ramp” needed to reach the programmed peak pulse amplitude may be determined by the IPG responsive to data supplied by the programming system. After reaching the programmed peak pulse amplitude, the IPG directs the electrodes to deliver at the programmed peak pulse amplitude for a predetermined number of stimulation pulses. After the predetermined number of stimulation pulses is reached, the IPG directs the electrodes, responsive to programming, stimulation commands, and/or received programming data, to deliver a stimulation pulse train in an “off ramp” manner such that the pulse amplitude decreases in predetermined increments from the programmed peak pulse amplitude to zero. As shown in FIG. 9, the pulse amplitude may drop, e.g., to zero, between each stimulation pulse.

FIG. 10 is a graph showing an exemplary session that may be delivered by the electrodes and IPG of the present invention. In this example, during a cycle, the IPG directs the electrodes, responsive to programming, stimulation commands, and/or received programming data, to deliver electrical stimulation for the cycle-on duration, followed by a cycle-off duration of no electrical stimulation. Illustratively, a session is a programmable duration of repetitive cycles and the session delay is the time delay between the receipt of the command by the IPG to start a session to the start of the first cycle. After a session is completed, IPG directs the electrodes, responsive to programming, stimulation commands, and/or received programming data, to stop delivering electrical stimulation until a new session begins.

Referring now to FIGS. 11-15, exemplary screen shots generated by user interface block 610 of software 600 are described for a stimulator system. FIG. 11 shows main program screen 1100 that is displayed to a physician running software-based programming system 600. Main program screen 1100 includes identification and status area 1102, electrode configuration area 1104, session parameters area 1106, impedance logging area 1108, settings area 1110, and buttons 1112.

In FIG. 11, identification and status area 1102 includes Subject ID, IPG Mode, Battery Status, Serial No., and Magnet Effect. Subject ID permits a user, e.g., a physician, to enter an ID, which is then displayed, for a subject having implanted electrodes and an IPG of the present invention. IPG Mode permits a user to turn the mode “ON”, such that the IPG implanted in the subject is activated, and turn the mode “OFF”, such that the IPG is deactivated. Battery Status displays the remaining battery power of the power supply in the IPG. Battery Status may be updated after a user interrogates the IPG to request updated battery status information. Serial No. displays the serial number assigned to the IPG implanted in the subject. Magnet Effect permits a user change how the IPG responds to sensing a magnetic field from a magnet, e.g., magnet 450. For example, a user may select “Stop Session Only”, such that the IPG will only stop a stimulation session upon sensing the magnet; the user may select “Start Session Only”, such that the IPG will only start a stimulation session upon sensing the magnet; the user may select “Start and Stop Session”, such that the IPG will interchangeably stop or stop a stimulation session each time the magnet is sensed; or the user may select “No Effect”, such that the IPG does not respond to sensing the magnet.

Electrode configuration area 1104 includes Stimulation Mode, Rate, right electrode lead display, left electrode lead display, Amplitude, Pulse Width, Impedance area, and Offset. Stimulation Mode permits a user to select a “Bilateral” mode where electrodes on two separate electrode leads stimulate tissue at the same time or a “Unilateral” mode where electrodes on only one electrode lead stimulate tissue. Rate permits a user to select a stimulation rate of any integer between, e.g., 1-40 Hz. Right electrode lead display shows an illustration of four electrodes (numbered 1-4) on the right electrode lead implanted within the subject while left electrode lead display shows the four electrodes (numbered 5-8) on the left electrode lead implanted within the subject. A user may select which electrode(s) stimulate in a session and may change the polarity of each electrode between positive and negative. In the illustrated embodiment, when a session begins, negative electrode 2 on the right lead and negative electrode 6 on the left lead transmit energy to target tissue to stimulate the tissue and positive electrodes 1 and 5, respectively, receive the energy after it has passed through the target tissue. Amplitude permits a user to adjust the pulse amplitude delivered by an electrode on a lead. A user may increase the pulse amplitude by selecting the Amplitude button and then pressing the corresponding up arrow button and decrease by pressing the corresponding down arrow button for the right or the left electrode lead. In one embodiment, the pulse amplitude increases or decreases by 0.1 mA when the corresponding arrow button is pressed by a user. Alternatively, a user may enter in the desired pulse amplitude using, for example, the keyboard on the computer. Pulse Width permits a user to adjust the pulse width delivered by an electrode on a lead. A user may increase the pulse width by selecting the Pulse Width button and then pressing the corresponding up arrow button and decrease by pressing the corresponding down arrow button for the right or the left electrode lead. In one embodiment, the pulse width increases or decreases by 1 μs when the corresponding arrow button is pressed by a user. Alternatively, a user may enter in the desired pulse width using, for example, the keyboard on the computer. Impedance area permits a user to select the Measure Impedance button which causes the programming system, via the external programmer, to command the IPG to run the routine to measure impedances and then transmit the measured impedances back to the programming system, via the external programmer. The measured impedances then are displayed for each electrode. Offset permits a user to offset the stimulation timing between the right and left electrodes.

Session parameters area 1106 includes Session, Cycle On, Cycle Off, On Ramp, and Off Ramp. The corresponding button for each of the parameters permits a user to adjust the timing for each parameter by selecting the button and then pressing the up or down arrows, or, alternatively, by selecting the corresponding button and entering the desired parameter using, for example, the keyboard on the computer.

Impedance logging area 1108 includes Log Impedance Daily, Daily Log Time, Log Impedance Matrix, and Matrix Log Period. Log Impedance Daily includes a button that permits a user to select “YES” or “NO”. If a user selects “YES”, the IPG will run the impedance test routine every day and store the measured impedance in its memory for transfer to the programming system software. Daily Log Time permits a user to adjust how many hours and minutes per day the IPG will log the measured impedance. Log Impedance Matrix permits a user to select “YES”, where the IPG will store the measured impedance in matrix form, and “NO” where the IPG will not store the measured impedance in matrix form. Matrix Log Period permits a user to select “Hourly”, “Daily”, or “Weekly”, whereby the IPG will store the measured impedance in a matrix every hour, every day, or every week, respectively.

Settings area 1110 includes Cumulative Max, Lockout Time, Session Delay, Pulse Train Balance, Interphase Period, Balance Mode, Voltage Limit, and Transpose L-R. Cumulative Max permits a user to select the maximum cumulative stimulation session minutes in an amount of days. Lockout Time permits a user to set a number of hours or minutes that a stimulation session may not be initiated. Session Delay permits a user to select a number of seconds that a session will be delayed after IPG receives a command to start a session. Pulse Train Balance permits a user to cause a pulse train balance mode to be “Enabled” or “Disabled”. The pulse train balance mode may be the mode described above with respect to FIG. 9. Interphase Period permits a user to adjust the time between stimulation pulses. Balance Mode permits a user to cause a balance mode to be “Active” or “Inactive”. The balance mode may be the mode described above with respect to FIG. 8. Voltage Limit permits a user to adjust the maximum voltage that may be supplied from the power source to the electrodes. In one embodiment, Voltage Limit may be set to “Automatic” such that the controller of the IPG determines the maximum voltage based on predetermined thresholds programmed therein. Transpose L-R permits a user to turn “ON” or “OFF” a mode that, when activated, causes stimulation to be interchanged between the electrodes on the right electrode lead and the electrodes on the left electrode lead.

Buttons 1112 include Interrogate, Program, Start Session, and Stop Session. When pressed, the “Interrogate” button causes the communications circuitry in the external programmer to transmit interrogation commands, such as requests for the (i) actual value of stimulation parameter(s) programmed in the IPG, (ii) battery voltage remaining in the IPG, (iii) data logged in the IPG, and (iv) IPG status data, to the communications circuitry in the IPG for processing by the IPG controller. The responsive data is then sent back to the software, via communications circuitry in the IPG and external programmer, for display on the user interface of the computer, such as main program screen 1100. The “Program” button, when pressed, causes the communications circuitry in the external programmer to transmit programming data to the communications circuitry in the IPG for processing by the IPG controller. Programming data may include, for example, adjustments made by the user to the various input areas in main program screen 1100. The “Start Session” button, when pressed, causes the communications circuitry in the external programmer to transmit a command to begin a treatment session, or optionally programming data that includes such a command, to the communications circuitry in the IPG at the selected stimulation parameters for processing by the IPG controller. The stimulation parameter data may be stored in the IPG controller such that future sessions will cause stimulation at the selected stimulation parameters. The “Stop Session” button, when pressed, causes the communications circuitry in the external programmer to transmit a command to stop a treatment session to the communications circuitry in the IPG for processing by the IPG controller.

FIG. 12 shows temporary program screen 1200 that is displayed to a physician running software-based programming system 600. Temporary program screen 1200 includes electrode configuration area 1202, session parameters area 1204, settings area 1206, and buttons 1208. Temporary program screen 1200 permits a user to adjust stimulation parameters on a temporary basis, e.g., for one or two sessions.

Electrode configuration area 1202 is similar to electrode configuration area 1104 of FIG. 11 and for conciseness, will not be described again in detail. Session parameters area 1204 is similar to session parameters area 1106 of FIG. 11, although session parameters area 1204 may include fewer parameters for user adjustment. Illustratively, session parameters area 1204 includes On Ramp and Off Ramp.

Settings area 1206 is similar to settings area 1110 of FIG. 11, although settings area 1206 may include fewer settings for user adjustment. Illustratively, settings area 1206 includes Pulse Train Balance, Interphase Period, Balance Mode, Voltage Limit, and Transpose L-R.

Buttons 1208 include Start Temporary Program, Stop Temporary Program, and Copy Changed Values to Main Screen. The “Start Temporary Program” button, when pressed, causes the communications circuitry in the external programmer to transmit a command to begin a treatment session to the communications circuitry in the IPG at the selected temporary stimulation parameters for processing by the IPG controller. The temporary stimulation parameter data may be stored in the IPG controller on a temporary basis such that future sessions will cause stimulation at the stimulation parameters programmed prior to receipt of the temporary stimulation parameters. The “Stop Temporary Program” button, when pressed, causes the communications circuitry in the external programmer to transmit a command to stop a treatment session to the communications circuitry in the IPG for processing by the IPG controller. The “Copy Changed Values to Main Screen” button, when pressed, causes software-based programming system 600 to copy the temporary stimulation parameters entered in screen 1200 into corresponding input areas in main program screen 1100 of FIG. 11.

FIG. 13 shows impedance screen 1300 that is displayed to a physician running software-based programming system 600. Impedance screen 1300 includes electrode configuration area 1302 and impedance matrix area 1304.

Electrode configuration area 1302 includes right electrode lead impedance display, left electrode lead impedance display, and Impedance area. Right electrode lead impedance display shows an illustration of four electrodes (numbered 5-8) on the right electrode lead implanted within the subject while left electrode lead impedance display shows the four electrodes (numbered 1-4) on the left electrode lead implanted within the subject. A user may select at which electrode(s) to measure impedance using the respective displays. Impedance area permits a user to select the “Measure Impedance” button which causes the programming system, via the external programmer, to command the IPG to run the routine to measure impedances at the electrodes selected in the lead displays and then transmit the measured impedances back to the programming system, via the external programmer. The measured impedances then is displayed for each electrode. Selection of electrodes on the lead displays for measuring impedance does not affect electrode configuration area 1104 of main program screen 1100 in FIG. 11.

Impedance matrix area 1304 includes an impedance matrix and a Measure Impedance Matrix button. When pressed, the “Measure Impedance Matrix” button causes the impedance matrix to be populated with the measured impedances in accordance with selections made at electrode configuration area 1302. In the illustrated embodiment, impedance between electrode 2 (selected to be negative) and electrode 1 (selected to be positive) on the left lead is measured to be 490 Ohms and impedance between electrode 6 (selected to be negative) and electrode 5 (selected to be positive) on the right electrode lead is measured to be 1355 Ohms. Thus, when the Measure Impedance Matrix button is pressed, the software causes 490 to be populated at the intersection of 2 negative and 1 positive and 1355 to be populated at the intersection of 6 negative and 5 positive in the impedance matrix. The impedance matrix also may display when an electrode is excluded or out of range.

FIG. 14 shows data review screen 1400 that is displayed to a physician running software-based programming system 600. Data review screen 1400 includes daily log area 1402 and data matrix area 1404.

Daily log area 1402 permits a user to view, on a day-by-day basis, Number of Daily Sessions, Total Daily Session Time, Daily Impedance, and Voltage. The date button permits a user to select a day and time such that a user may view stored data from the selected day/time. The “Number of Daily Sessions” area displays the number of treatment sessions that were started for the selected day. The “Total Daily Session Time” area displays the number of minutes of treatment sessions for the selected day. The “Daily Impedance” area displays the measured impedance of the right and left electrode lead for the selected day. The “Voltage” area displays the measured voltage remaining in the IPG power supply at the end of the selected day.

Data matrix area 1404 includes a data matrix and a “Get Stored Data” button. When pressed, the “Get Stored Data” button, causes the communications circuitry in the external programmer to transmit a request for stored data to the communications circuitry in the IPG for processing by the IPG controller. The IPG controller retrieves the stored data from its memory and causes the communications circuitry in the IPG to transmit the stored data to the communications circuitry in the external programmer for display on data review screen 1400. The data matrix is populated with received stored data in the appropriate row and column corresponding to the electrode configuration. The data matrix also may display when an electrode is disabled.

FIG. 15 shows data graphs screen 1500 that is displayed to a physician running software-based programming system 600. Data graphs screen 1500 includes session time graph 1502 and impedance graph 1504. Session time graph 1502 displays the total daily session time on a daily basis, as retrieved from stored data in the IPG. In the illustrated embodiment, session time 1506 shows that the patient used the stimulation system for 60 minutes on the first day and then did not use the stimulation system for the next 15 days. Impedance graph 1504 displays the daily impedance for the right and left electrode lead on a daily basis, as retrieved from stored data in the IPG. In the illustrated embodiment, right impedance 1508 shows that the measured impedance for the electrodes on the right electrode lead was about 12,000 ohms over three days, while left impedance 1510 shows that the measured impedance for the electrodes on the left electrode lead was about 1400 ohms over three days. When pressed, the “Get Stored Data” button, causes the communications circuitry in the external programmer to transmit a request for stored data to the communications circuitry in the IPG for processing by the IPG controller. The IPG controller retrieves the stored data from its memory and causes the communications circuitry in the IPG to transmit the stored data to the communications circuitry in the external programmer for display on data graphs screen 1500.

As will be readily understood by one of ordinary skill in the art, a user may enter data into the user interface using suitable mechanisms known in the art, such as, entering numbers, letters, and/or symbols via a keyboard or touch screen, mouse, touchpad, selection from a drop-down menu, voice commands, or the like.

While various illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true scope of the invention. 

What is claimed is:
 1. A neuromuscular electrical stimulation system for rehabilitating skeletal muscles, the system comprising: a lead having one or more electrodes configured to be implanted in or adjacent to nervous tissue associated with one or more skeletal muscles associated with local segmental control of a lumbar spine; an implantable pulse generator coupled to the one or more electrodes, the implantable pulse generator having a programmable controller configured to be programmed to cause the one or more electrodes to electrically stimulate the nervous tissue to induce muscle contraction to restore neural control and rehabilitate the one or more skeletal muscles to thereby improve lumbar spine stability; and an external transmitter coupled to the implantable pulse generator.
 2. The system of claim 1, wherein the lead comprises a first fixation element coupled to the lead, the first fixation element angled distally relative to the lead, and a second fixation element coupled to the lead distal to the first fixation element, the second fixation element angled proximally relative to the lead, wherein the first and second fixation elements are configured to sandwich an anchor site therebetween.
 3. The system of claim 1, wherein the one or more electrodes are configured to be implanted in or adjacent to at least one of nervous tissue, a muscle, a ligament, or a joint capsule.
 4. The system of claim 1, wherein the one or more electrodes are configured to be implanted in or adjacent to a medial branch of a dorsal ramus nerve that innervates the multifidus muscle.
 5. The system of claim 1, wherein the programmable controller is programmed to cause the one or more electrodes to electrically stimulate the nervous tissue at a pulse amplitude between 0.1-7 mA, a pulse width between 20-500 μs, and a stimulation rate between 1-20 Hz.
 6. The system of claim 1, wherein the programmable controller is configured to be programmed to cause the one or more electrodes to electrically stimulate the nervous tissue to induce muscle contraction to restore neural control and rehabilitate the one or more skeletal muscles selected from at least one of the following muscles: multifidus, transverse abdominus, quadratus lumborum, psoas major, internus abdominus, obliquus externus abdominus, or erector spinae.
 7. The system of claim 1, wherein the external transmitter is configured to control the implantable pulse generator by transferring a stimulation command to the implantable pulse generator, the stimulation command comprising at least one of: a command to start a treatment session or stop the treatment session; a command to provide a status of the implantable pulse generator; or a request to conduct an impedance assessment.
 8. The system of claim 1, wherein the implantable pulse generator comprises a first transceiver coupled to a first antenna, and wherein the external transmitter comprises a second transceiver coupled to a second antenna, such that the external transmitter is configured to control the implantable pulse generator via bi-directional communication between the first and second transceivers and the first and second antennas.
 9. The system of claim 1, wherein the external transmitter comprises a first telemetry system electrically coupled to a first coil, and wherein the implantable pulse generator comprises a second telemetry system electrically coupled to a second coil, such that the external transmitter is configured to charge the implantable pulse generator via energy transfer from the first telemetry system and coil to the second telemetry system and coil.
 10. The system of claim 9, wherein energy is transferred from the first telemetry system and coil to the second telemetry system and coil via inductive coupling.
 11. The system of claim 1, further comprising an external programmer configured to transfer programming data to the implantable pulse generator, the programming data comprising at least one of: pulse amplitude, pulse width, stimulation rate, stimulation frequency, ramp timing, cycle timing, session timing, or electrode configuration, wherein the external transmitter controls the implantable pulse generator to electrically stimulate the nervous tissue in accordance with the programming data.
 12. The system of claim 11, further comprising a computer-readable non-transitory medium having program instructions that, when executed by a processor of the external programmer, permit a user to select, adjust, and display the programming data based on user input.
 13. The system of claim 1, further comprising one or more sensors coupled to the programmable controller, the one or more sensors configured to sense muscle contraction and to generate a sensor signal based on the muscle contraction.
 14. The system of claim 13, wherein at least one of the one or more sensors comprises at least one of an accelerometer, a minute ventilation system, a pressure sensor, a movement sensor, or a strain gauge.
 15. The system of claim 13, wherein the sensor signal is indicative of patient compliance.
 16. A method of rehabilitating skeletal muscles, the method comprising: implanting a lead having one or more electrodes in or adjacent to nervous tissue associated with one or more skeletal muscles associated with local segmental control of a lumbar spine; implanting an implantable pulse generator coupled to the one or more electrodes; programming the implantable pulse generator to restore neural control and rehabilitate the one or more skeletal muscles; and controlling the implantable pulse generator to cause the one or more electrodes to electrically stimulate the nervous tissue to induce muscle contraction via the one or more electrodes, thereby restoring neural control and rehabilitating the one or more skeletal muscles to thereby improve lumbar spine stability.
 17. The method of claim 16, further comprising transferring energy from an external transmitter to the implantable pulse generator via inductive coupling.
 18. The method of claim 16, further comprising one or more sensors coupled to a programmable controller of the implantable pulse generator, the method further comprising sensing muscle contraction via the one or more sensors and generating a sensor signal based on the muscle contraction.
 19. The method of claim 18, wherein at least one of the one or more sensors comprises at least one of an accelerometer, a minute ventilation system, a pressure sensor, a movement sensor, or a strain gauge.
 20. The method of claim 18, wherein the sensor signal is indicative of patient compliance. 